1. Field of the Invention
This invention relates to a wafer structure, and more particularly relates to a die seal ring that can effectively prevent a die from being damaged by the stress caused by sawing of the die and to a wafer wherein each die has such a die seal ring.
2. Description of Related Art
Along with the development in technology, integrated circuit devices have been widely applied in our daily life. Manufacture of an IC device generally includes three stages, production of a semiconductor wafer, fabrication of integrated circuits on the dies on the wafer and packaging of the dies cut from the wafer. The first step in the packaging stage is to cut the dies from the wafer.
A semiconductor wafer has a plurality of perpendicularly crossing scribe lines to separate a plurality of dies. After integrated circuits are formed on the dies, a diamond blade can be used to saw the wafer along the scribe lines to obtain single dies. Since various material layers are formed on the wafer, the stress caused by blade sawing easily causes damages like chipping and peeling to the dies, especially when there is a low-k material formed on the dies. Thus, the device reliability is lowered.
Another way to cut the dies is laser grooving, which still has certain problems however. For example, when a metal material has been formed on the wafer, the metal is difficult to remove completely by laser and forms debris that contaminates the dies. Moreover, a heat effect area is formed beside the scribe lines lowering the reliability of the dies. In addition, the price of a laser cutting system is 2-3 time higher than that of a diamond blade cutting system, so that the manufacturing cost is much increased.
Some methods capable of preventing damages like chipping and peeling of the die in the sawing have been provided. For example, as shown in FIG. 1, U.S. Pat. No. 6,876,062 teaches a structure 100 formed at a die corner and including an irregular seal ring 102 and a dummy pattern 103 to prevent the die from being damaged by the stress, wherein the dummy pattern 103 may be formed at both sides of the seal ring 102.
Though the above structure 100 effectively prevents the die from being damaged by the stress caused by sawing, the fabricating process adversely gets more complicated.